The simian immunodeficiency virus (SIV) produces an infection in rhesus monkeys that is remarkably similar to that caused by HIV in humans, including, as we have found recently, a wasting condition similar to that seen in young persons with HIV. SIV also cause serum micronutrient deficiencies, despite an apparently adequate intake. Because of the rapid progression of SIV, and the clear end points of nutritional parameters, biological markers, and survival, as well as a controlled dietary intake, the SIV-infected rhesus monkey is an ideal model to study unanswered nutrition questions in HIV/AIDS related to unintentional weight loss and low serum micronutrient levels. Specifically, to what extent are weight loss, or in the case of youngsters, failure to gain weight, and micronutrient deficiencies caused by reduced dietary intake or advancing HIV infection? How do changes in these nutritional parameters relate to viral load? CD4 counts? Occurrence of opportunistic infections? Are there changes in body composition, i.e. the relative amounts of fat and lean body mass (skeletal muscle), even when body weight is unchanged or slowly increasing? Can an intervention with an anabolic steroid (oxandrolone) cause weight gain in the face of advancing HIV infection? To this end, we plan to: 1) Document the natural history of weight gain/loss and micronutrient deficiency in SIV-infected (SIVmac239) male juvenile rhesus/macaques compared to age0matched uninfected control animals; and 2) Conduct two interventions in SIV-infected macaques with oxandrolone, a growth-promoting anabolic steroid, and a highly supplemented (HS) micronutrient intake with 3 times the RDAs for most vitamins and increased amounts of vitamins B12 (intramuscularly) and E and trace minerals (selenium, zinc and iron), along with the standard diet. These studies will allow us to address unanswered questions in HIV/AIDS about nutritional deficiencies and wasting. In addition, we will be able to test the efficacy of nutritional interventions without the confounding factors that such studies would entail in human HIV infection.